Hundreds of Southwest Airlines pilots picketed at Dallas Love Field on Wednesday as the pilots have been without a contract since 2012.

The informational picket, organized by the Southwest Airlines Pilots’ Association, occurred as the union continues contract negotiations with the Dallas-based carrier. Pilots stood silently in the ticketing and baggage claim areas at Love Field, holding signs that said “No confidence in SWA management” and “The heart of Southwest is under attack.”

“The pilots of Southwest simply want to remain contractually on par with our fellow professional pilots at other companies,” said Southwest Airlines Pilots’ Association president Jon Weaks. “Management actions, however, continue to foster labor discord.”

The two sides entered federal mediation in 2014 and last year, pilots rejected a proposed contract that included pay raises totaling 17.6 percent but created subsets for international and Boeing 737-MAX flying. In May, SWAPA sued Southwest for “unlawful tactics” during contract talks, alleging that Southwest has threatened to operate the new Boeing 737-MAX aircraft even if it does not reach a new contract with its pilots.

The union has held several pickets including one in Chicago at Southwest’s shareholder meeting. At the pickets, the pilots have been joined by flight attendants and mechanics, unions that have also been in lengthy contract talks with the carrier.

“I am proud of our pilots and the leadership they provide,” said Vice President Labor Relations Mike Ryan. “Even with our disagreements, we are partners in this process and need to work through the remaining issues at the negotiating table, rather than in public forums.”